Optical system, lens module and electronic device

Abstract

An optical system, a lens module, and an electronic device. The number of lenses with refractive power in the optical system is four. Along the optical axis direction from the object side to the image side, it sequentially includes: a first lens with negative refractive power, the object side surface is concave near the circumference, and the image side surface is convex near the circumference; a second lens with refractive power; a third lens with positive refractive power, the object side surface is convex near the optical axis, and the image side surface is concave near the optical axis; a fourth lens with positive refractive power, the object side surface is convex near the optical axis, and the image side surface is concave near the optical axis. The optical system satisfies the relational expressions: 0.9 < FNO < 1.3, 160° < FOV < 177°. This optical system has a larger aperture, a larger field of view angle, and higher image resolution, which helps to improve image quality and user experience.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging technology, and particularly relates to an optical system, lens module and electronic device. Background Technology

[0002] With the development of technology, especially in the fields of computer vision and image processing, the demand for high-performance optical systems is constantly increasing. Time-of-Flight (ToF) optical systems are mainly used for depth sensing and 3D imaging, and are widely used in autonomous driving, robot navigation, virtual reality, and augmented reality. However, existing optical systems still have a relatively small shooting range, and it is difficult to ensure miniaturization when acquiring a larger field of view. They also have relatively low illumination, and the image quality in low-light environments often fails to meet the requirements of modern applications. Therefore, developing a lens with a large aperture and a large field of view is particularly important. Summary of the Invention

[0003] The purpose of this invention is to provide an optical system, lens module, and electronic device, specifically a ToF optical system with a larger aperture, a larger field of view, and higher image resolution.

[0004] To achieve the objectives of this invention, the following technical solution is provided:

[0005] In a first aspect, the present invention provides an optical system comprising four lenses having refractive power, which, from the object side to the image side along the optical axis, sequentially include: a first lens having negative refractive power, wherein the object side is concave near the circumference and the image side is convex near the circumference; a second lens having refractive power; a third lens having positive refractive power, wherein the object side is convex near the optical axis and the image side is concave near the optical axis; and a fourth lens having positive refractive power, wherein the object side is convex near the optical axis and the image side is concave near the optical axis.

[0006] The optical system provided in this application achieves high-quality imaging in low light by combining the refractive power of four lenses. The first lens has negative refractive power, with its object-side surface concave at the circumference and its image-side surface convex at the circumference, which facilitates the convergence of light rays over a large field of view. The second lens has refractive power, which helps correct aberrations generated by the front lens. The third lens has positive refractive power, with its object-side surface convex at the paraxial position and its image-side surface concave at the paraxial position, which helps delay the light rays entering the system from the front lens and reduces the angle of incidence. The fourth lens has positive refractive power, which helps correct spherical aberration, coma, and distortion generated by the front lens group, shortens the overall length, suppresses the light emission angle, and facilitates a large range of light rays incident on the image plane.

[0007] In one embodiment, the optical system satisfies the relationship: 0.9 < FNO < 1.3, 160° < FOV < 177°; where FNO is the f-number of the optical system and FOV is the maximum field angle of the optical system. When the above relationship is satisfied, the characteristics of a large aperture of the optical system can be ensured, allowing the optical system to have sufficient light input to make the captured image clearer; and the optical system can have the characteristics of a large field angle, with a larger shooting range, and the optical system has the characteristics of high pixels and high definition.

[0008] In a second aspect, the present invention further provides a lens module, which includes the optical system according to any one of the embodiments in the first aspect and a photosensitive chip, and the photosensitive chip is disposed on the image side of the optical system.

[0009] In a third aspect, the present invention further provides an electronic device, which includes a housing and the lens module in the second aspect, and the lens module is disposed in the housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0011] Figure 1 It is a schematic structural diagram of the optical system of the first embodiment;

[0012] Figure 2 It is an aberration diagram of the optical system of the first embodiment; <​​​​​​​​​​​​​​​​​​​​​​​​​This is a schematic diagram of the optical system in the fifth embodiment;

[0020] Figure 10 Aberration diagram of the optical system in the fifth embodiment;

[0021] Figure 11 This is a schematic diagram of the optical system in the sixth embodiment;

[0022] Figure 12 Aberration diagram of the optical system in the sixth embodiment;

[0023] Figure 13 This is a schematic diagram of the optical system in the seventh embodiment;

[0024] Figure 14 Aberration diagram of the optical system in the seventh embodiment;

[0025] Figure 15 This is a schematic diagram of a lens module provided in an embodiment of the present invention;

[0026] Figure 16 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In a first aspect, the present invention provides an optical system comprising four lenses having refractive power, which, from the object side to the image side along the optical axis, sequentially include: a first lens having negative refractive power, wherein the object side is concave near the circumference and the image side is convex near the circumference; a second lens having refractive power; a third lens having positive refractive power, wherein the object side is convex near the optical axis and the image side is concave near the optical axis; and a fourth lens having positive refractive power, wherein the object side is convex near the optical axis and the image side is concave near the optical axis.

[0029] In the optical system provided by this application, by matching the refractive powers of four lenses, a high-quality imaging effect in low light can be achieved. Among them, the first lens has a negative refractive power, its object side is concave at the circumference, and its image side is convex at the circumference, which is conducive to the incidence and convergence of light in a large field of view. The second lens has a refractive power, which helps to correct the aberration generated by the front lens. The third lens has a positive refractive power, its object side is convex at the paraxial region, and its image side is concave at the paraxial region, which is conducive to delaying the light incident from the front lens into the system and delaying the angle. The fourth lens has a positive refractive power, which is conducive to correcting the spherical aberration, coma and distortion generated by the front group of lenses, can shorten the total length, and at the same time can suppress the light exit angle, and is also conducive to the incidence of light in a large range onto the image plane.

[0030] In one embodiment, the optical system satisfies the relationship: 0.9 < FNO < 1.3; where FNO is the f-number of the optical system. When the above relationship is satisfied, the optical system can have the characteristic of a large aperture, allowing the optical system to have sufficient light input and making the captured image clearer. Optionally, the value of FNO can be 0.901, 0.930, 0.949, 0.950, 1.000, 1.050, 1.150, 1.200, 1.250, 1.299.

[0031] In one embodiment, the optical system satisfies the relationship: 160° < FOV < 177°; where FOV is the maximum field of view angle of the optical system. When the above relationship is satisfied, the optical system can have the characteristic of a large field of view angle, with a larger shooting range, and the optical system has the characteristics of high pixels and high definition. Optionally, the value of FOV can be 160.001, 163.739, 164.939, 167.292, 169.773, 170.265, 170.543, 173.233, 176.617, 176.999.

[0032] In one embodiment, the optical system satisfies the relationship: 140° < FOV / FNO < 180°. When the above relationship is satisfied, the lens can achieve large-field imaging while ensuring a large light input, making the image clearer. Optionally, the value of FOV / FNO can be 140.001, 141.294, 148.056, 156.011, 159.326, 161.688, 166.568, 173.784, 179.519, 179.999.

[0033] In one embodiment, the optical system satisfies the relation: 2.6 < TTL / ImgH < 2.8; where TTL is the distance from the object side surface of the first lens to the imaging surface on the optical axis, and ImgH is half of the image height corresponding to the maximum field angle of the optical system. When the above relation is satisfied, the optical system has an ultra-thin characteristic, and it is more advantageous for shooting medium focal length distance scenes and miniaturizing the imaging device. Optionally, the value of TTL / ImgH can be 2.601, 2.634, 2.676, 2.703, 2.754, 2.762, 2.776, 2.782, 2.792, 2.799.

[0034] In one embodiment, the optical system satisfies the relation: 1.7 < ImgH / BL < 2.2; where BL is the minimum distance from the image side surface of the fourth lens to the imaging surface. When the above relation is satisfied, on the one hand, there is a larger focusing range during the debugging process of the lens module end, and on the other hand, the lens module may actually be used to shoot a target board, and a sufficient back focal length ensures that the lens can find the best focus point in this case. Optionally, the value of ImgH / BL can be 1.701, 1.797, 1.865, 2.029, 2.035, 2.037, 2.057, 2.058, 2.119, 2.199.

[0035] In one embodiment, the optical system satisfies the relation: 1.5 < ImgH / EPD < 2.2; where EPD is the entrance pupil diameter of the optical system. When the above relation is satisfied, on the premise of a certain eye pupil size, the size of the screen can be restricted, and the selection direction of the screen can be clarified. Optionally, the value of ImgH / EPD can be 1.501, 1.594, 1.674, 1.717, 1.724, 1.758, 1.864, 2.027, 2.115, 2.199.

[0036] In one embodiment, the optical system satisfies the relation: -2.9 < f1 / f < -2; where f is the effective focal length of the optical system, and f1 is the effective focal length of the first lens. When the above relation is satisfied, by controlling the ratio of the effective focal length of the first lens to the effective focal length of the entire optical system within a certain range, the refractive power of the first lens will not be too strong for the effective focal length of the entire optical system, and the high-order spherical aberration can be corrected, so that the optical system has good imaging quality. Optionally, the value of f1 / f can be -2.001, -2.011, -2.035, -2.118, -2.192, -2.342, -2.545, -2.668, -2.859, -2.899.

[0037] In one embodiment, the optical system satisfies the relation: 5 < |f2| / f < 40; where f2 is the effective focal length of the second lens. When the above relation is satisfied, by controlling the ratio of the effective focal length of the second lens to the effective focal length of the entire optical system within a certain range, the refractive power of the second lens will not be too strong for the effective focal length of the entire optical system, and it can correct the high-order spherical aberration, enabling the optical system to have good imaging quality. Optionally, the value of |f2| / f can be 5.001, 5.119, 5.506, 5.579, 5.829, 6.513, 7.685, 10.485, 37.560, 39.999.

[0038] In one embodiment, the optical system satisfies the relation: 2.5 < f3 / f < 9; where f3 is the effective focal length of the third lens. When the above relation is satisfied, by controlling the ratio of the effective focal length of the third lens to the effective focal length of the entire optical system within a certain range, the refractive power of the third lens will not be too strong for the effective focal length of the entire optical system, and it can correct the high-order spherical aberration, enabling the optical system to have good imaging quality. Optionally, the value of f3 / f can be 2.601, 2.667, 2.831, 2.843, 3.005, 3.215, 3.812, 5.466, 8.644, 8.999.

[0039] In one embodiment, the optical system satisfies the relation: 1.1 < f4 / f < 1.4; where f4 is the effective focal length of the fourth lens. When the above relation is satisfied, by controlling the ratio of the effective focal length of the fourth lens to the effective focal length of the entire optical system within a certain range, the refractive power of the fourth lens will not be too strong for the effective focal length of the entire optical system, and it can correct the high-order spherical aberration, enabling the optical system to have good imaging quality. Optionally, the value of f4 / f can be 1.101, 1.125, 1.170, 1.260, 1.273, 1.301, 1.305, 1.338, 1.340, 1.399.

[0040] In one embodiment, the optical system satisfies the relation: -1.7 < R1 / f < -1.2; where R1 is the curvature radius of the object side surface of the first lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the curvature radius of the first lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the first lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lens, thereby enabling the optical system to have good imaging quality. Optionally, the value of R1 / f can be -1.201, 1.309, -1.422, -1.468, -1.485, -1.547, -1.575, -1.598, -1.654, -1.699.

[0041] In one embodiment, the optical system satisfies the relationship: 6 < |R2| / f < 28; R2 is the radius of curvature of the image side of the first lens at the optical axis. When the above relationship is satisfied, by controlling the ratio of the radius of curvature of the first lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the first lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lens, so that the optical system has good imaging quality. Optionally, the value of |R2| / f can be 6.001, 7.164, 7.465, 10.615, 10.725, 11.173, 11.734, 17.643, 24.600, 27.999.

[0042] In one embodiment, the optical system satisfies the relationship: 5 < |R3| / f < 20; R3 is the radius of curvature of the object side of the second lens at the optical axis. When the above relationship is satisfied, by controlling the ratio of the radius of curvature of the second lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the second lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lens, so that the optical system has good imaging quality. Optionally, the value of |R3| / f can be 5.001, 5.168, 5.761, 7.586, 7.826, 8.178, 9.548, 13.434, 18.904, 19.999.

[0043] In one embodiment, the optical system satisfies the relationship: 2.7 < |R4| / f < 40; R4 is the radius of curvature of the image side of the second lens at the optical axis. When the above relationship is satisfied, by controlling the ratio of the radius of curvature of the second lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the second lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lens, so that the optical system has good imaging quality. Optionally, the value of |R4| / f can be 2.701, 2.784, 5.737, 6.074, 6.974, 7.084, 15.252, 22.844, 35.912, 39.999.

[0044] In one embodiment, the optical system satisfies the relationship: 1.2 < R5 / f < 2.8; R5 is the radius of curvature of the object side of the third lens at the optical axis. When the above relationship is satisfied, by controlling the ratio of the radius of curvature of the third lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the third lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lens, so that the optical system has good imaging quality. Optionally, the value of R5 / f can be 1.201, 1.298, 1.397, 1.427, 1.503, 1.532, 1.695, 2.086, 2.673, 2.799.

[0045] In one embodiment, the optical system satisfies the relation: 3.2 < R6 / f < 5; R6 is the curvature radius of the image side surface of the third lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the curvature radius of the third lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the third lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lenses, so that the optical system has good imaging quality. Optionally, the value of R6 / f can be 3.201, 3.471, 3.885, 3.891, 3.935, 4.175, 4.260, 4.531, 4.750, 4.999.

[0046] In one embodiment, the optical system satisfies the relation: 1.5 < f / R7 < 2; R7 is the curvature radius of the object side surface of the fourth lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the curvature radius of the fourth lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the fourth lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lenses, so that the optical system has good imaging quality. Optionally, the value of f / R7 can be 1.501, 1.587, 1.682, l.687, 1.715, 1.784, 1.816, 1.946, 1.987, 1.999.

[0047] In one embodiment, the optical system satisfies the relation: 1 < R8 / f < 2; R8 is the curvature radius of the image side surface of the fourth lens at the optical axis. When the above relation is satisfied, by controlling the ratio of the curvature radius of the fourth lens to the effective focal length of the entire optical system within a certain range, the astigmatism of the fourth lens can be within a reasonable range, and it can effectively balance the astigmatism generated by the previous lenses, so that the optical system has good imaging quality. Optionally, the value of R8 / f can be 1.001, 1.047, 1.134, 1.200, 1.334, 1.362, 1.494, 1.695, 1.882, 1.999.

[0048] In one embodiment, the optical system satisfies the relation: 0.18 < (R6 - R5) / f3 < 1.1. When the above relation is satisfied, the refractive power of the optical system is reasonably distributed, so that the optical system has a high aberration correction ability while maintaining miniaturization, and better manufacturability can be obtained. Optionally, the value of (R6 - R5) / f3 can be 0.181, 0.184, 0.574, 0.689, 0.743, 0.815, 0.897, 0.967, 1.071, 1.099.

[0049] In one embodiment, the optical system satisfies the relation: 1.3 < ΣCT / ΣET < 1.6; where ΣCT is the sum of the central thicknesses of the first lens to the fourth lens on the optical axis, and ΣAT is the sum of the air spacings of the first lens to the fourth lens on the optical axis. When the above relation is satisfied, sufficient air intervals can be ensured between the lenses and between the last lens and the imaging surface, which is not only beneficial to the structural design and assembly process of the lens barrel and the lenses, but also can better balance distortion; in addition, there is a larger forming and debugging process space, avoiding the risk of stray light caused by appearance problems of the lenses, and achieving a better match between the chief ray angle and the photosensitive chip. Optionally, the value of ΣCT / ΣET can be 1.301, 1.352, 1.396, 1.437, 1.466, 1.474, 1.487, 1.502, 1.575, 1.599.

[0050] In one embodiment, the optical system satisfies the relation: 1 < CT2 / CT1 < 1.7; where CT1 is the central thickness of the first lens on the optical axis, and CT2 is the central thickness of the second lens on the optical axis. When the above relation is satisfied, the central thicknesses of the first lens and the second lens on the optical axis are reasonably controlled, which is beneficial to ensuring the process requirements for the molding of two plastic lenses and is also beneficial to correcting off-axis coma. Optionally, the value of CT2 / CT1 can be 1.001, 1.054, 1.169, 1.299, 1.358, 1.464, 1.550, 1.594, 1.683, 1.699.

[0051] In one embodiment, the optical system satisfies the relation: 2.1 < CT3 / CT2 < 3.2; where CT3 is the central thickness of the third lens on the optical axis. When the above relation is satisfied, the central thicknesses of the second lens and the third lens on the optical axis are reasonably controlled, which is beneficial to ensuring the process requirements for the molding of two plastic lenses and is also beneficial to correcting off-axis coma. Optionally, the value of CT3 / CT2 can be 2.101, 2.143, 2.544, 2.740, 2.837, 2.914, 2.992, 3.043, 3.126, 3.199.

[0052] In one embodiment, the optical system satisfies the relation: 2.5 < CT3 / CT4 < 3.1; where CT4 is the central thickness of the fourth lens on the optical axis. When the above relation is satisfied, the central thicknesses of the third lens and the fourth lens on the optical axis are reasonably controlled, which is beneficial to ensuring the process requirements for the molding of two plastic lenses and is also beneficial to correcting off-axis coma. Optionally, the value of CT3 / CT4 can be 2.501, 2.526, 2.672, 2.695, 2.734, 2.896, 2.973, 3.072, 3.097, 3.099.

[0053] In one embodiment, the optical system satisfies the relation: 0.8 < CT2 / CT4 < 1.3. Satisfying the above relation and reasonably controlling the central thicknesses of the second lens and the fourth lens on the optical axis is conducive to ensuring the process requirements for the molding of the two plastic lenses and is also conducive to correcting off-axis coma. Optionally, the value of CT2 / CT4 can be 0.801, 0.830, 0.926, 0.950, 1.027, 1.063, 1.085, 1.134, 1.247, 1.299.

[0054] In one embodiment, the optical system satisfies the relation: 𝟎.𝟔 < (CT3 + CT4) / ΣCT < 0.71. Satisfying the above relation enables the thicknesses of the lenses to be complementary to each other, basically forming a "thin-thin-thick-thin" configuration, which has a good effect on canceling aberrations such as spherical aberration, astigmatism, and chromatic aberration, and also has a good complementary effect in extreme environments such as high and low temperatures. Optionally, the value of (CT3 + CT4) / ΣCT can be 0.601, 0.623, 0.649, 0.655, 0.677, 0.685, 0.696, 0.701, 0.704, 0.709.

[0055] In one embodiment, the optical system satisfies the relation: 2.7 < CT3 / ET3 < 3.3; where ET3 is the edge thickness of the third lens at the edge. Satisfying the above relation can ensure that the thickness of the third lens is evenly distributed at different positions, reduce the influence of the thickness non-uniformity of the third lens on the imaging quality of the optical system, and at the same time help improve the molding yield of the third lens. Optionally, the value of CT3 / ET3 can be 2.701, 2.7𝟗4, 2.883, 2.956, 2.957, 2.968, 3.066, 3.14𝟑, 3.238, 3.299.

[0056] In one embodiment, the optical system satisfies the relation: 0.3 < SR / SD8 < 0.5; where SR is the effective semi-aperture of the aperture stop in the optical system and SD8 is the effective semi-aperture of the image side of the fourth lens. Satisfying the above relation can, on the one hand, effectively control the vignetting value of the optical system and intercept the light rays with poor imaging quality, thereby improving the resolution of the optical system; on the other hand, it can avoid the step difference caused by the aperture difference of each lens and improve the stability of assembly. Optionally, the value of SR / SD8 can be 0.301, 0.331, 0.357, 0.381, 0.403, 0.428, 0.437, 0.445, 0.478, 0.499.

[0057] In one embodiment, the optical system satisfies the relation: 1.7 < SD1 / SD2 < 1.9; where SD1 is the effective semi-aperture of the object side of the first lens, and SD2 is the effective semi-aperture of the image side of the first lens. Satisfying the above relation facilitates controlling the maximum light passing aperture of the first lens to achieve the characteristics of a large aperture and a relatively high relative illumination. Optionally, the value of SD1 / SD2 can be 1.701, 1.736, 1.768, 1.775, 1.782, 1.792, 1.825, 1.854, 1.878, 1.899.

[0058] In one embodiment, the optical system satisfies the relation: 1 < SD1 / ImgH < 1.1. Satisfying the above relation enables a reasonable configuration of the ratio between half of the maximum effective aperture of the object side of the first lens and half of the image height corresponding to the maximum field angle of the optical system, which is beneficial for reasonably controlling the size of the object side of the first lens and achieving miniaturization of the optical system. Optionally, the value of SD1 / ImgH can be 1.001, 1.014, 1.024, 1.031, 1.042, 1.049, 1.056, 1.069, 1.074, 1.099.

[0059] In one embodiment, the optical system satisfies the relation: 1.1 < SD1 / SD8 < 1.2. Satisfying the above relation is beneficial for reducing the main ray incident angle, improving the relative illumination, and enhancing the imaging quality. Optionally, the value of SD1 / SD8 can be 1.101, 1.120, 1.137, 1.148, 1.155, 1.167, 1.168, 1.172, 1.190, 1.199.

[0060] In one embodiment, the optical system satisfies the relation: 2.7 < R6 / SD6 < 3.3; where SD6 is the effective semi-aperture of the image side of the third lens. Optionally, the value of R6 / SD6 can be 2.701, 2.786, 2.857, 2.972, 2.975, 3.070, 3.098, 3.133, 3.271, 3.299.

[0061] In a second aspect, the present invention further provides a lens module, which includes the optical system according to any one of the embodiments in the first aspect and a photosensitive chip, and the photosensitive chip is disposed on the image side of the optical system.

[0062] In a third aspect, the present invention further provides an electronic device, which includes a housing and the lens module according to the second aspect, and the lens module is disposed inside the housing.

[0063] First Embodiment

[0064] Please refer to Figure 1 and Figure 2The optical system 10 of this embodiment includes, from the object side to the image side, the following components in sequence:

[0065] The first lens L1 has negative refractive power. Near the optical axis 101, the object-side surface S1 is concave and the image-side surface S2 is convex; near the circumference, the object-side surface S1 is concave and the image-side surface S2 is convex.

[0066] The second lens L2 has negative refractive power. Near the optical axis 101, the object-side surface S3 is convex and the image-side surface S4 is concave; near the circumference, the object-side surface S3 is concave and the image-side surface S4 is convex.

[0067] The third lens L3 has positive refractive power. Near the optical axis 101, the object-side surface S5 is convex and the image-side surface S6 is concave; near the circumference, the object-side surface S5 is convex and the image-side surface S6 is concave.

[0068] The fourth lens L4 has positive refractive power. Near the optical axis 101, the object-side surface S7 is convex and the image-side surface S8 is concave; near the circumference, the object-side surface S7 is convex and the image-side surface S8 is concave.

[0069] In this system, the first lens L1 to the fourth lens L4 are all made of plastic. In other embodiments, the lens material can also be glass, or a glass-plastic hybrid, where some lenses are plastic and others are glass. Furthermore, the optical system 10 includes an aperture stop STO, a filter IR, and an imaging surface IMG. The aperture stop STO is disposed on the object-side surface S3 of the second lens L2 to control the amount of light entering the lens. The filter IR includes an object-side surface S9 and an image-side surface L10, with the object-side surface S9 facing the fourth lens L4. The effective pixel area of ​​the photosensitive chip is located on the imaging surface IMG.

[0070] The IR filter can be an infrared cut-off filter, used to filter out infrared light, allowing only visible light (wavelength 380nm-780nm) to enter the imaging surface (IMG). The infrared cut-off filter is made of glass and can be coated on the lens. Alternatively, in other embodiments, the IR filter can also be an infrared-passing filter, used to filter visible light and allow only infrared light to pass through, suitable for infrared imaging, etc.

[0071] Table 1 shows the characteristics of the optical system 10 of this embodiment. The Y-radius in Table 1 is the radius of curvature of the object-side or image-side surface of the corresponding surface number at the optical axis 101. Surface number S1 and surface number S2 are the object-side surface S1 and image-side surface S2 of the first lens L1, respectively. That is, in the same lens, the surface with the smaller surface number is the object-side surface, and the surface with the larger surface number is the image-side surface. The first value in the "thickness" parameter column of the first lens L1 is the thickness of the lens on the optical axis 101, and the second value is the distance from the image-side surface of the lens to the subsequent optical surface (the object-side surface or aperture surface of the subsequent lens) on the optical axis 101.

[0072] Table 1

[0073]

[0074] As shown in Table 1, f is the effective focal length of the optical system 10, FNO is the aperture number of the optical system 10, FOV is the maximum field of view of the optical system 10, TTL is the distance from the object side surface S1 of the first lens L1 to the imaging surface IMG on the optical axis 101, and ImgH is half of the image height corresponding to the maximum field of view of the optical system.

[0075] In this embodiment, the first lens L1 to the fourth lens L4 are all aspherical lenses. The surface shape x of the aspherical surface can be defined using, but is not limited to, the following aspherical formula:

[0076]

[0077] Where x is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex on the axis, h is the distance from the corresponding point on the aspherical surface to the optical axis 101, c is the curvature of the vertex of the aspherical surface, k is the conic coefficient, and Ai is the coefficient corresponding to the i-th higher-order term in the aspherical surface shape formula. Table 1b gives the higher-order coefficients k, A4, A6, A8, A10, A12, A14, A16, A18, A20, A22, A24, A26, A28, and A30 that can be used for the aspherical mirror in the first embodiment.

[0078] Table 2

[0079]

[0080]

[0081] Figure 2 Figure (a) shows the longitudinal spherical aberration curves of the optical system of the first embodiment at wavelengths of 960.0000 nm, 940.000 nm, and 920.0000 nm. The horizontal axis along the X-axis represents the focal point shift in mm, and the vertical axis along the Y-axis represents the normalized field of view. The longitudinal spherical aberration curves represent the deviation of the focal point after light of different wavelengths passes through the lenses of the optical system. Figure 2 As can be seen from (a), the spherical aberration value of the optical system in the first embodiment is better, indicating that the imaging quality of the optical system in this embodiment is better.

[0082] Figure 2Figure (b) also shows an astigmatism curve of the optical system of the first embodiment at a wavelength of 940.000 nm, where the horizontal axis along the X-axis represents the focal shift in mm, and the vertical axis along the Y-axis represents the half-image height in mm. In the astigmatism curve, T represents the curvature of the imaging plane IMG in the meridional direction, and S represents the curvature of the imaging plane IMG in the sagittal direction. Figure 2 As can be seen in (b), the astigmatism of the optical system is well compensated.

[0083] Figure 2 Figure (c) also shows a distortion curve of the optical system of the first embodiment at a wavelength of 940.000 nm. The horizontal axis along the X-axis represents distortion, and the vertical axis along the Y-axis represents half-image height, in mm. The distortion curve represents the distortion magnitude corresponding to different field of view angles. Figure 2 As can be seen in (c), the distortion of the optical system is well corrected at a wavelength of 940.000 nm.

[0084] Depend on Figure 2 As can be seen from (a), (b) and (c), the optical system of this embodiment has small aberrations, good imaging quality, and excellent imaging performance.

[0085] Second Embodiment

[0086] Please refer to Figure 3 and Figure 4 The difference between the structure of the optical system 10 in this embodiment and that in the first embodiment is that the image-side surface S2 of the first lens L1 at the optical axis is concave; the object-side surface S3 of the second lens L2 at the optical axis is concave, and the image-side surface S4 at the circumference is concave; the object-side surface S7 of the fourth lens L4 at the circumference is concave, and the image-side surface S8 at the circumference is convex.

[0087] Table 3 shows the characteristics of the optical system 10 in this embodiment. The meanings of each parameter are the same as those in the first embodiment, and will not be repeated here.

[0088] Table 3

[0089]

[0090] Table 3 shows the higher-order coefficients that can be used for each aspherical mirror in the second embodiment, wherein each aspherical surface shape can be defined by the formula given in the first embodiment.

[0091] Table 4

[0092]

[0093] Figure 4The diagrams show the longitudinal spherical aberration, astigmatism, and distortion curves of the optical system according to the second embodiment. Figure 4 As can be seen from the aberration diagram, the longitudinal spherical aberration, field curvature, and distortion of the optical system are all well controlled, thus the optical system of this embodiment has good imaging quality.

[0094] Third Embodiment

[0095] Please refer to Figure 5 and Figure 6 The difference between the structure of the optical system 10 in this embodiment and that in the first embodiment is that the image-side surface S2 of the first lens L1 at the optical axis is concave; the object-side surface S3 of the second lens L2 at the optical axis is concave, and the image-side surface S4 at the circumference is concave; the object-side surface S7 of the fourth lens L4 at the circumference is concave, and the image-side surface S8 at the circumference is convex.

[0096] Table 5 shows the characteristics of the optical system 10 in this embodiment. The meanings of each parameter are the same as those in the first embodiment, and will not be repeated here.

[0097] Table 5

[0098]

[0099] Table 6 shows the higher-order coefficients that can be used for each aspherical mirror in the third embodiment, wherein each aspherical surface shape can be defined by the formula given in the first embodiment.

[0100] Table 6

[0101]

[0102]

[0103] Figure 6 The diagram shows the longitudinal spherical aberration, astigmatism, and distortion curves of the optical system according to the third embodiment. Figure 6 As can be seen from the aberration diagram, the longitudinal spherical aberration, field curvature, and distortion of the optical system are all well controlled, thus the optical system of this embodiment has good imaging quality.

[0104] Fourth embodiment

[0105] Please refer to Figure 7 and Figure 8The optical system 10 in this embodiment differs from that in the first embodiment in that the image-side surface S2 of the first lens L1 at the optical axis is concave; the second lens L2 has positive refractive power, the object-side surface S3 at the optical axis is concave, the image-side surface S4 at the optical axis is convex, the object-side surface S3 at the circumference is convex, and the image-side surface S4 at the circumference is concave; the fourth lens L4 has the object-side surface S7 at the circumference is concave, and the image-side surface S8 at the circumference is convex.

[0106] Table 7 shows the characteristics of the optical system 10 in this embodiment. The meanings of each parameter are the same as those in the first embodiment, and will not be repeated here.

[0107] Table 7

[0108]

[0109] Table 8 shows the higher-order coefficients that can be used for each aspherical mirror in the fourth embodiment, wherein each aspherical surface shape can be defined by the formula given in the first embodiment.

[0110] Table 8

[0111]

[0112] Figure 8 The diagram shows the longitudinal spherical aberration, astigmatism, and distortion curves of the optical system according to the fourth embodiment. Figure 8 As can be seen from the aberration diagram, the longitudinal spherical aberration, field curvature, and distortion of the optical system are all well controlled, thus the optical system of this embodiment has good imaging quality.

[0113] Fifth Embodiment

[0114] Please refer to Figure 9 and Figure 10 The difference between the structure of the optical system 10 in this embodiment and that in the first embodiment is that the image-side surface S2 of the first lens L1 at the optical axis is concave; the object-side surface S3 of the second lens L2 at the optical axis is concave; and the object-side surface S7 of the fourth lens L4 at the circumference is concave, while the image-side surface S8 at the circumference is convex.

[0115] Table 9 shows the characteristics of the optical system 10 in this embodiment. The meanings of each parameter are the same as those in the first embodiment, and will not be repeated here.

[0116] Table 9

[0117]

[0118] Table 10 shows the higher-order coefficients that can be used for each aspherical mirror in the fifth embodiment, wherein each aspherical surface shape can be defined by the formula given in the first embodiment.

[0119] Table 10

[0120]

[0121]

[0122] Figure 10 The diagram shows the longitudinal spherical aberration, astigmatism, and distortion curves of the optical system according to the fifth embodiment. Figure 10 As can be seen from the aberration diagram, the longitudinal spherical aberration, field curvature, and distortion of the optical system are all well controlled, thus the optical system of this embodiment has good imaging quality.

[0123] Sixth Embodiment

[0124] Please refer to Figure 11 and Figure 12 The difference between the structure of the optical system 10 in this embodiment and that in the first embodiment is that the image-side surface S2 of the first lens L1 at the optical axis is concave; the object-side surface S3 of the second lens L2 at the optical axis is concave; and the object-side surface S7 of the fourth lens L4 at the circumference is concave, while the image-side surface S8 at the circumference is convex.

[0125] Table 11 shows the characteristics of the optical system 10 in this embodiment. The meanings of each parameter are the same as those in the first embodiment, and will not be repeated here.

[0126] Table 11

[0127]

[0128] Table 12 shows the higher-order coefficients that can be used for each aspherical mirror in the sixth embodiment, wherein each aspherical surface shape can be defined by the formula given in the first embodiment.

[0129] Table 12

[0130]

[0131] Figure 12 The diagram shows the longitudinal spherical aberration, astigmatism, and distortion curves of the optical system according to the sixth embodiment. Figure 12 As can be seen from the aberration diagram, the longitudinal spherical aberration, field curvature, and distortion of the optical system are all well controlled, thus the optical system of this embodiment has good imaging quality.

[0132] Seventh Embodiment

[0133] Please refer to Figure 13 and Figure 14 The difference between the structure of the optical system 10 in this embodiment and that in the first embodiment is that the object-side surface S3 of the second lens L2 at the optical axis is concave.

[0134] Table 13 shows the characteristics of the optical system 10 in this embodiment. The meanings of each parameter are the same as those in the first embodiment, and will not be repeated here.

[0135] Table 13

[0136]

[0137] Table 14 shows the higher-order coefficients that can be used for each aspherical mirror in the seventh embodiment, wherein each aspherical surface shape can be defined by the formula given in the first embodiment.

[0138] Table 14

[0139]

[0140]

[0141] Figure 14 The diagram shows the longitudinal spherical aberration, astigmatism, and distortion curves of the optical system according to the seventh embodiment. Figure 14 As can be seen from the aberration diagram, the longitudinal spherical aberration, field curvature, and distortion of the optical system are all well controlled, thus the optical system of this embodiment has good imaging quality.

[0142] Table 15 shows the values ​​of various relationships in the optical system 10 of the first embodiment to the seventh embodiment, where E1 is the first embodiment, E2 is the second embodiment, and so on up to E7 for the seventh embodiment.

[0143] Table 15

[0144]

[0145]

[0146] By satisfying the above formula, the refractive force distribution can be made uniform and reasonable, aberrations can be easily corrected, and image quality can be well performed. The optical system 10 provided in the above embodiments can meet the characteristics of large aperture and large field of view. The optical system 10 can ensure that it can provide sufficient light intake and high-definition imaging effect while ensuring a compact and stable structure.

[0147] refer to Figure 15This invention also provides a lens module 20, which includes the optical system 10 and a photosensitive chip 201 as described in any of the preceding embodiments. The photosensitive chip 201 is disposed on the image side of the optical system 10, and the two can be fixed by a bracket. The photosensitive chip 201 can be a CCD sensor (Charge Coupled Device) or a CMOS sensor (Complementary Metal Oxide Semiconductor). Generally, during assembly, the imaging surface (IMG) of the optical system 10 overlaps with the photosensitive surface of the photosensitive chip 201. By employing the aforementioned optical system 10, the lens module 20 can achieve a large aperture and a large field of view while ensuring that the lens module 20 also has the characteristics of compact structure, stability, and miniaturization.

[0148] refer to Figure 16 This invention also provides an electronic device 30. The electronic device 30 includes a housing 310 and a lens module 20 as described in the preceding embodiments, with the lens module 20 mounted on the housing 310. The electronic device 30 can be, but is not limited to, a vehicle lens, VR (Virtual Reality) glasses, a smartphone, a smartwatch, an e-book reader, a tablet computer, a biometric device (such as a fingerprint recognition device or an iris recognition device), a PDA (Personal Digital Assistant), etc. Because the lens module 20 can meet the requirements of a large aperture and clear imaging, when using the lens module 20, the electronic device 30 can achieve a large aperture and a wide field of view while ensuring the miniaturization of the lens module 20, thus reserving space for other components in the electronic device.

[0149] The above description discloses only some preferred embodiments of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art can understand that implementing all or part of the above embodiments and making equivalent changes in accordance with the claims of the present invention still fall within the scope of the present invention.

Claims

1. An optical system characterized by comprising: The number of lenses with refractive power is four, which successively include along the optical axis direction from the object side to the image side: A first lens with negative refractive power, the object side surface is concave near the optical axis and concave near the circumference, and the image side surface is convex near the circumference; A second lens with refractive power; A third lens with positive refractive power, the object side surface is convex near the optical axis and the image side surface is concave near the optical axis; A fourth lens with positive refractive power, the object side surface is convex near the optical axis and the image side surface is concave near the optical axis; The optical system satisfies the relational expressions: 0.9 < FNO < 1.3, 160° < FOV < 177°; where, FNO is the aperture number of the optical system, and FOV is the maximum field angle of view of the optical system.

2. The optical system of claim 1, wherein The optical system satisfies the relational expression: 140° < FOV / FNO < 180°.

3. The optical system of claim 1, wherein The optical system satisfies the relational expressions: 2.6 < TTL / ImgH < 2.8; and / or, 1.7 < ImgH / BL < 2.2; and / or, 1.5 < ImgH / EPD < 2.2; where, TTL is the distance from the object side surface of the first lens to the imaging surface on the optical axis, ImgH is half of the image height corresponding to the maximum field angle of view of the optical system, BL is the minimum distance from the image side surface of the fourth lens to the imaging surface, and EPD is the entrance pupil diameter of the optical system.

4. The optical system of claim 1, wherein The optical system satisfies the relational expressions: -2.9 < f1 / f < -2; and / or, 5 < |f2| / f < 40; and / or, 2.5 < f3 / f < 9; and / or 1.1 < f4 / f < 1.4; where, f is the effective focal length of the optical system, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, and f4 is the effective focal length of the fourth lens.

5. The optical system of claim 1, wherein The optical system satisfies the relational expressions: -1.7 < R1 / f < -1.2; and / or, 6 < |R2| / f < 28; and / or, 5 < |R3| / f < 20; and / or, 2.7 < |R4| / f < 40; and / or, 1.2 < R5 / f < 2.8; and / or, 3.2 < R6 / f < 5; and / or, 1.5 < f / R7 < 2; and / or, 1 < R8 / f < 2; where, f is the effective focal length of the optical system, R1 is the curvature radius of the object side surface of the first lens at the optical axis; R2 is the curvature radius of the image side surface of the first lens at the optical axis, R3 is the curvature radius of the object side surface of the second lens at the optical axis; R4 is the curvature radius of the image side surface of the second lens at the optical axis, R5 is the curvature radius of the object side surface of the third lens at the optical axis; R6 is the curvature radius of the image side surface of the third lens at the optical axis, R7 is the curvature radius of the object side surface of the fourth lens at the optical axis; R8 is the curvature radius of the image side surface of the fourth lens at the optical axis.

6. The optical system of claim 1, wherein The optical system satisfies the relation: 0.18 < (R6 - R5) / f3 < 1.1; where, R5 is the curvature radius of the object side surface of the third lens on the optical axis; R6 is the curvature radius of the image side surface of the third lens on the optical axis, and f3 is the effective focal length of the third lens.

7. The optical system of claim 1, wherein The optical system satisfies the relation: 1.3 < ΣCT / ΣET < 1.6; and / or, 1 < CT2 / CT1 < 1.7; and / or, 2.1 < CT3 / CT2 < 3.2; and / or, 2.5 < CT3 / CT4 < 3.1; and / or, 0.8 < CT2 / CT4 < 1.3; and / or, 0.6 < (CT3 + CT4) / ΣCT < 0.71; and / or, 2.7 < CT3 / ET3 < 3.3; where, ΣCT is the sum of the central thicknesses of the first lens to the fourth lens on the optical axis, ΣAT is the sum of the air spacings of the first lens to the fourth lens on the optical axis, CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, CT3 is the central thickness of the third lens on the optical axis, CT4 is the central thickness of the fourth lens on the optical axis, and ET3 is the edge thickness of the third lens at the edge.

8. The optical system according to claim 1, characterized in that, The optical system satisfies the relation: 0.3 < SR / SD8 < 0.5; and / or, 1.7 < SD1 / SD2 < 1.9; and / or, 1 < SD1 / ImgH < 1.1; and / or, 1.1 < SD1 / SD8 < 1.2; and / or, 2.7 < R6 / SD6 < 3.3; where, SR is the effective semi-aperture of the aperture stop in the optical system, SD8 is the effective semi-aperture of the image side surface of the fourth lens, SD1 is the effective semi-aperture of the object side surface of the first lens, SD2 is the effective semi-aperture of the image side surface of the first lens, ImgH is half of the image height corresponding to the maximum field angle of the optical system, R6 is the curvature radius of the image side surface of the third lens on the optical axis, and SD6 is the effective semi-aperture of the image side surface of the third lens.

9. A lens module, characterized by, Comprising the optical system according to any one of claims 1 to 8 and a photosensitive chip, the photosensitive chip is arranged on the image side of the optical system.

10. An electronic device, comprising: The electronic device includes a housing and the lens module according to claim 9, the lens module is arranged in the housing.

Images